Telephone system



Sept. 3, 1940. w. BENNETT 2,213,511

A TELEPHONE SYSTEM v Filed Oct. 3l, 1939 16 Sheets-Sheet l Sept. 3, 1940.

w. BENNETT TELEPHONE SYSTEM Filed Oct. 3l, 1959 16 Sheets-Sheet 2 INI/ENTO nf BENNETT 6? a. amd

AHORA/Ek w'. BENNETT TELEPHONE SYSTEM Sept. 3, 1940.

Filed Oct. 31, 1939 16 Sheets-Sheet 3v /NVENTOR W BENNETT ATTORNEY Sept. 3, 1940.

w, BENNETT TELEPHONE SYSTEM Filed Oct. 5l. 1939 16 Sheets-Sheet 5 .Sb h

/Nl/ENTOR By W BENNETT 6? 6. M

AoRA/Ey A Sept. 3, 1940.

W. BENNETT TELEPHONE SYSTEM Filed oct. 31, 1959 16 Sheets-Sheet` 6 /Nl/EA/TOR n. BENNETT By @aw ATTORNEY Sept. 3, 1940. wY BENNETT 2,213,511

TELEPHONE SYSTEM Filed Oct. 3l, 1939 16 Sheets-Sheet 7 SPEECH LEVEL INDICA TOR N0. 2

/Nl/ENTOR n. BENNETT ATTORNEY Sept 3, 1940. w. BENNETT TELEPHONE SYSTEM Filed Oct. 3l, 1939 16 Sheets-Sheet 8 '//WENTOR W BENNE'T By @a M AHORA/5y Sept. 3, 1940.

W. BENNET'I,

TELEPHONE SYSTEM Filed Oct. 3l, 19459 16 Sheets-Sheet 9 IN1/E NTO/P nf BEN/V577 6? 6, 6m#

Sept. 3, 1940. w. BENNETT 2,213,511

TELEPHONE SYSTEM Filed Oct. 5l, 1939 16 Sheets-Sheet 10 ATTORNEY sept. 3, 1940.

w. BENNETT TELEPHONE SYSTEM 16 Sheets-Sheet 1l Filed Oct. 3l, 31.939

Sept. 3, 1940. w. BENNETT TELEPHONE SYSTEM Filed oct. s1, 1939 16 Sheets-Sheet l2 /NVE/VTOR By W BEN/V577 @aw S. Nwk N v ATTORNEY Sept. 3, 1940. `w BENNETT 2,213,511

TELEPHONE SYSTEM Filed Oct. 3l, 1939 16 Sheets-Sheet 13 WEA/ro@ W BENNE T7 Sept. 3, 1940. w. BENNETT TELEPHONE SYSTEM Filed Oct. 3l, 1939 16 Sheets-Sheet 14 ATTORNEY Sept. 3, 1940. w. BENNETT TELEPHONE SYSTEM Filed oet. s1, 1939 A16 Sheets-Sheet 16 NMS ATTORNEY Patented Sept. 3, 1940 UNITED STATES naar PATENT or-Flce TELEPHONE vSYSTEM William Bennett, Brooklyn, N. Y., assgnor to Bell Telephone Laboratories,

Incorporated, New

This invention relates to telephone exchange systems and more particularly to systems in which any subscriber by calling a. designated directory number may obtain a connection with a central information announcing bureau from which announcements, such as weatherI fore-l casts, crop reports, results of sporting events, etc., are automatically made. 'I'he object of the invention is to enable the '10 information announcements to be automatically and efficiently transmitted to as many subscribers in an exchange area or a plurality of such areasl as concurrently initiate calls for such Service. t This object is attained in accordance with the 16 present invention by the pro-vision of announcement trunks accessible from the terminal banks of selector switches of local oices or from the terminal banks of selector switches of tandem oflices which are multipled to a trunk outgoing 20 to a central announcing bureau. Associated with the announcement trunks is a distributing circuit which is responsive to the seizure of any one of the announcement trunks to eiect the cut-through of the speech transmission circuit over eachv calling` trunk and to cause the opening of each transmission circuit after an interval suflicient to enable each calling subscriber to hear one or more complete announcements transmitted from the central bureau. The trunk circuit incoming to the central bureau terminates at the bureau in a control circuit with which three announcing machines of the magnetizable tape type and two vSpeech level indicators and alarm circuits are associable. Of the three announcing machines one is? normally running andtwohave recorded on their tapes the latest information to be transmitted, such, for example, as the latest weather report received from the United States Weather Bureau. One of these two machines has its speech output circuit normally connected through suitable amplifiers to the incoming trunk circuit so that upon the cut-through of connections from one or more subscribers lines such subscribers are enabled to hear the announcement.transmitted from such machine. The second of the two machines is held as a spare in readiness for a service connection to the incoming trunk should the machine inthe Aspeech level indicators which periodicallyl 55 makes a check to determine if there is a speech The third machine is held in requires la new recording.

output therefrom. and if the output speech level is within desired lower and an upper volume limits. If the level is too low or there. is no speech` output the control circuit is operated to .transfer the connection to the incoming trunk from the 5 output circuit of the machine in service to the output circuit of the spare machine; to connect the output circuit of such spare machine to the other speech level indicator which similarly checks the volume of its; output and to operate a 10 minor alarm to indicate the failure of one of. the machines and the fact that the spare machine is in service. If the speech level indicator nds that the speech level of the spare machine is not correct, it operates the control circuitto 15 remove such machine from service and to operate a major alarm to indicate that there is' no machine inservice. The monitoring operators turret is provided with in-service and out-oforder lamps individual to each machine which 20 are lighted when the corresponding machine is in service or out of order.

The control circuit is arranged to connect the three machines in pairs for service and spare service in accordance with a definite pattern so 25 that when the No. 1 machine is: vin service the No. 2 machine is on spare service, when. the No.

2 is in service the No. 3 machine is on spare service and when the No.3 machine is in service the No. 1 machine is'on spare service.v The oper- 30 ators turret is provided with an erase key, which when operated removes the machine which is on l spare service from such service and erases the record from the tape of such machine and from theA tape of the reserve machine and is also pro- 35 vided with a recording key which connects the monitoring operators recording transmitter with such machines for placing a new record on their tapes. The machines which have thus hadnew records placed on their tapes cannot again be 40 placed in service until their output circuits have been connected to the speech level indicator which is not at the ltime being used for monitoring on the machine still in service. To monitor on newly recorded machines. the' monitoring turret 45 is provided 'with a monitoring jack to which the operators headset may be 'connected and with a monitoring key individual to each machine. During recording lamps individual to each machine are lighted on the turret to indicate which machines are being recorded. Provision is made to flash" the recording lamp of any machine which has been removed 'from service and re- If the speech level of either newly recorded machine is not correct either a high or low level lamp on the turret will be lighted and the operator Will thereupon erase the record on such machine and re-record. When both machines are correctly recorded the operator may place one of such machines in service and the other on spare service and transfer the machine in service to reserve by the operation of a cut-in service key on her turret.

- The operators turret is also provided! with jacks individual tof'the machines into which she may plug her recording transmitter for giving Y.

manual announcements directly to calling subscribers in the event of machine failures-,"such announcements beinfr monitored by one of Ythe speech level indicators for correct Vvolume and being at the same time recorded on machines which are at the time available for recording.`

A transfer key lis also provided' on amaintenance panel to enable the manual transfer ofthe vload from the machine in service to the Spare'ma-- In some instances it i-s desirable to extend the information service to subscribers whose lines terminate in the oices of another-exchange area. In this case it is not economical to extend direct trunks from such ofnces to the exchange area in which the information bureau is located. Therefore, for such extended service the local announcement trunks of the remote exchange area are terminated in an auxiliary control circuit located in such area and have associated with them a common distributing circuit. The auxiliary control circuit comprises two parallel trunk channels each provided with supervisory equipment, an amplifier, a speech detecting relay, a timing circuit and alarm equipment. The output ends of both channels are connected together through a Wheatstone bridge to the multipled outgoingends of the announcement trunks and the input ends ofthe channels extend as two cable pairs to a branched trunk circuit in the office in which the information announcing bureau is located. Each branch of this trunkcircuit is provided with a repeating coil and with a supervisory relay, the input windings of the repeating coils being both connected to the trunk terminating in the control circuit of the central bureau. Both channels of the auxiliary control circuit normally function at the same time so that announcements from the central bureau are transmitted thereover to all calling subscribers lines in the remote exchange area.

Whenever calls for information service are initiated in the remote exchange area announcement trunks in such area are seized and through their associated distributing circuit a start signal is transmitted to the auxiliary control circuit. This start signal causes the establishment of supervisory circuits over both cable pairs extending to the branched trunk circuitat the central bureau to signal the control circuit at the central bureau that a call is waiting. If the central bureau circuit is not functioning so that announcements may not be made, the branched trunk circuit receives a signal therefromwhichoperates a relay therein to open the supervisory circuits extending to the auxiliary control circuit in the remote area. If either supervisory circuit is not completed a minor alarm is lgiven at the auxiliary control circuit and if neither circuit is completed, a major. alarm is given. The closure of either supervisory circuit is also effective to transmit a signal to the distributing circuit of the remote area Vto cut through the calling announcement trunks and to time the duration of the cutthrough period.

As previously stated each channel of the auxiliary control circuit is provided with an amplifier and a speech detection relay. If speech reception is transmitted properly, through the amplier of each channel, the speech detection relays will 'both operate. For determining ifY speech is being properly transmitted, each channel is provided with a timing circuitk which duringl each cycle will rst prepare the circuit of a test'relay associated withthe channel which will operate only if the speech detection relay is at the time unoperated, thereby indicating a failure of speech transmission over the channel. If the test relay operates, it is instrumental at a later period of the timing cycle to operate the alarm equipment associated with the channel which has failed. The timing circuit during each cycle is also arranged to restore the speech detection relay of its channel for reoperation. If both channels when tested are found to be transmitting no speech current, a major alarm is operated and the associated distributing circuit is signaled to prevent the further cut-through of calling announcement trunks.

A clearer conception of the scope and purpose of the invention will be, obtained from a consideration of the following description taken in connection with the attached drawings in which:

Fig. 1 shows the line of a subscriber A terminating in an originating office X of a iirst exchange area, the schematic representation of a line-finder, a link circuit having a line-finder selector and a sender selector by means of which the line may become associated with a central oflice sender indicated by the box in the lower por-tion of the gure and the schematic representation of a district selector and oice selector by means of which the calling line mayl be further extended; l i

Fig. 2 shows an outgoing announcement trunk accessible from the terminal banks of oiflce selectors one of which is disclosed in Fig. 1 and a distributing circuit common to a plurality of announcement trunks;

Fig. 3 shows the three announcement machines associable with the central information announcing bureau, one machine and the associated power supply, control and amplier circuits being shown in full and the similar circuits of the other two machines being represented by the boxes in the lower portion of the figure; v

Figs. 4 to 13, inclusive, taken together show the circuits of the control circuit at the central information announcing bureau;

Fig. 14 shows one of the speech level indicators associable with the control circuit;

Fig. 15 shows the line of a subscriber B terminating in an originating ofce Y of a second exchange area, the schematic representation of a line-finder, district selector and office selector by means of which the calling line may be extended, a schematic representation of one of the announcement trunks accessible from the office selector and the associated distributing circuit and a portion of the auxiliary control circuit of the exchange area; v

Fig. 16 showsat the left of the vertical dotdash line the remaining portion of the auxiliary control circuit and at the right ,of the dot-.dash line the branched trunk circuit at the rst yexchange area in which interexchange trunks extending between the exchange areas terminate and which is connected to the control circuit of the first exchange area; and

Fig, 17 is a chart indicating the manner in which the several figures of the drawings should be assembled to disclose the detailed circuits of the invention.

General description The apparatus of the originating offices shown in Figs. 1 and 15 is of the well-known panel type. The line finders |01 and |505, selector switches |02, |03, |502 and |503, and the link circuit |04 of Fig. l may be of the same type and function in the same manner as the similar apparatus disclosed and described in Patent No. 1,690,206, granted to A. Raynsford on November 6, 1928. The sender |05 of Fig. 1 may be of the same type as disclosed in Patent No. 1,505,171, issued to F. A. Stearn on August 19, 1924. To simplify the drawings, these pieces of apparatus have been schematically represented and reference may be had to the above-identified patents for a full detailed disclosure thereof. To simplify the drawings, the link circuit and sender have been omitted from Fig. 15 but it is to be understood that a link circuit and sender similar to those represented in Fig. 1 would be employed.

While the invention has been illustrated in connection with switching apparatus of the panel type, it is to be understood that the announcement trunks of either or both exchange areas could terminate as well in oice links and connector circuits of originating oices of the well-known cross-bar type or in the distant cnice selectors of tandem offices. The invention is equally ap plicable by slight modification of the announce@ ment trunks to systems having originating offices of the manual or step-by-step type.

The speech level indicators one of which is disclosed in detail in Fig. 14 and the other of which is indicated by the box |00 of Fig. 7 are of the general type disclosed in Patent No.

2,119,212, granted May 31, 1938 to H. Kahl.

The magnetic tape announcing machines, one of which is schematically illustrated in Fig. 3 and designated by the numeral 300, are of the type disclosed in the application of C. C. Towne, Serial No. 284,155, file-d July 13, 1939..

In Fig. 2, one of the announcement trunks outgoing from the bank terminals of selectors, such as |03, of the dial switching office X is shown in detail. Other similar trunks, sufficient in number to handle the peak demand for the information service, terminating in the same or other ofce selectors of ofiice X and in office selectors of other similar originating oiices or in the distant office selectors of tandem offices would be provided. These trunk circuits are all multiplied together at their distant ends and connected to a trunk 20|, 232 extending into the control circuit of Figs. 4 to 13, inclusive. The distributing circuit shown in the right portion of Fig. 2 is common to all of these announcement trunks and to the trunks incoming from other exchange areas, such as the trunk shown in the right portion of Fig. i6.

The trunk and distributing circuit indicated by the box |500 of Fig. l5 and located in another exchange area to which the information service is supplied are identical to the trunk and distributing circuit disclosed in Fig. 2.

Initiation of a call It will be assumed that a subscriber A whose line terminates in ofce X of the exchange area in which the information bureau is located initiates a call, for example, to obtain the latest weather report apert'aining to the particular section in which the exchange area is located. The subscriber upon removing his receiver from the switchhook causes the setting of the brushes of the line finder |0| upon the terminals of the calling line and the extension of circuits from the calling line and district selector |02 over the wipers of the line-iinder selector |50 and sender selector of the link circuit |00 to an idle sender l05. Upon the seizure of the sender the sender transmits a dial tone` to the calling subscribers line in the usual manner to apprise the subscriber that he may commence dialing. v The subscriber then proceeds to dial the digits of the directo-ry number assigned to the central weather forecasting bureau which it will be assumed is WEather 6-1212 thereby setting the registers of the sender to record the office and numerical designations of the weather bureau number.

As soon as the sender has registered the wanted line designation it proceeds in the well-known manner in accordance with the oflice code registered therein to set the district selector |02 and the office selector |03 to select an idle announcement trunk extending toward the central bureau. It will be assumed that the trunk disclosed in Fig. 2 is idle and is seized. for service by the oiice selector |03. During the setting of if is established between the trunk of Fig. 2 and the sender 0/1 which may be traced in part from battery through the left winding of relay 200, inner left back contacts of relay 20 l, upper back contacts of cut-through relay 202, upper left winding of repeating coil 203, tip trunk conductor 200, tip brushes of selectors |00 and |02, right and lower left contacts of cam |06, thence through the link circuit |04, winding of the sender stepping relay (not shown), thence returning through the link circuit over the upper left and right contacts of cam |01, ring brushes of selectors |02 and |03, ring trunk conductor 205, lower left winding of repeating coil 203, outer lower back contacts of ground through the right winding ofrelay 200.

The stepping relay of the sender and relay 200 v now operate and since calls to the weather bureau are handled by the sender in the same manner as calls to a terminating oice having a call indicator and the control sequence switch of the sender has therefore been set in response to the registration of the office code to control the sender to transmit call indicator code impulses in accordance with t'he numerical registration set up in the sender, the sender is now prepared to transmit such impulses. Relay 200 upon operating establishes a circuit from ground over its front contacts, the right back contacts of relay 206, the right contacts of interrupter 207, as soon as the cam of the interrupter closes such contacts, winding of relay 200, through resistance 209 to battery. Relay 208 thereupon operates, locks contacts of relay 20| to ground to operate the peg count meter; at' its inner upper front contacts, closes a start circuit over the inner upper normal back contacts of relay 200 and the outer left back contacts of key 2I2, to battery through the winding of start relay 2 I3 of the common distributing circuit and at its inner lower iront contacts prepares a circuit for relay 20|. After an interval sufiicient to permit the sender to make the usual trunk guard test, interrupter 201 closes its left contacts, thereby completing the circuit of relay 20|, which may be traced from ground over the back contacts of relay 2I0, middle lower front contacts of relay 208, left contacts of interrupter 201, inner lower front contacts of relay 208, inner left normal contacts of relay 206, through the winding of relay 20| to battery. Relay 20| now operates, locks in a circuit from battery through its winding, the inner left normal contacts of relay 205, the outer right contacts of relay 20|, to ground over the middle upper front contacts of relay 208; at its outer left back contacts opens the circuit of the peg count meter; at its inner back contacts disconnects the windings of relay 200 from the tip and ring conductors 204 and 205 of the trunk and connects these conduct'ors over its inner front contacts to a dry bridge including the windings of polarized relay 2I4 and resistance 2 I 5.

Relay 200 now releases without affecting the circuits previously established and the stepping relay of the sender also releases to start the impulser of the sender to transmit relay call indicator impulses which are absorbed by the dry bridge including the windings of polarized relay 2 I4. When the sender transmits the iinal heavy positive impulse relay 2|4 responds thereto closing a circuit from ground over its front contacts to battery through the' left winding of relay 206 which thereupon operates, locks over its right winding and inner right front contacts to ground at the middle upper front contacts of relay 208,

and at its inner left transfer contacts transfers the locking ground for relay 20| from the middle upper front contacts of relay 208 to the front contacts of relay 2I4. Upon the termination of the heavy positive impulse, relay 2I4 releases whereupon relay 20| releases to disconnect the winding of relay 2I4 from the trunk conductors and to reconnect the windings of relay 200 thereto. Following the sending of the relay call indicator impulses, the sender is advanced to the talking selection position in turn advancing the district selector sequence switch to the talking position and itself being disconnected from the established connection and restored to normal condition.

With the sequence switch of the district selector in the talking position and relay 20| released a circuit is established from battery through the left winding of relay 200, thence as traced over trunk conductor 204 and the tip brushes of selector switches |03 and |02, upper contacts of cam |06, upper right winding of repeating coil |08, winding of polarized supervisory relay I 09, lower right winding of repeating coil |08, lower contacts of cam |01, thence as traced to ground through the right winding of relay 200. Relay 200 now reoperates but the current does not flow in the proper direction through the winding of polarized relay |08 to cause its operationy at this time. Relay 200 upon operating establishes a circuit from ground over its contacts, the middle right front contacts of relay 206, to battery through the upper winding of relay 2I0, which in turn operates, locks over its lower winding and l'IIS lower front contacts to ground at the outer right front contacts of relay 206; at its upper back contacts opens the holding circuit of relay 208,

and at its upper front contacts closes a new holding circuit for relay 208, whereby relay 208 is now held operated by the operating ground supplied for relay 2I0 over the contacts of relay 200. Relay 208, being slow to release, does not release during this transfer of its holding ground.

Relay 206, upon operating, also establishes a ringing tone circuit which maybe traced from the source of ringing current 2I8, over the lower back contacts of relay 2I9, the outer left front contacts of relay 206, the inner lower back contacts of relay 202, thence through the right windings of repeating coil 203, over the next to outer upper back contacts of relay 202, to ground at the upper back contacts of relay 2I9, whereby ringing tone is transmitted inductively to the V trunk circuit, through the right windings of repeating coil |08 at the district selector, and then inductively over the calling line loop as a signal that a connection has been completed from .the calling line to an idle announcement trunk.

Since the trunk circuit is a two-Wire circuit, it is necessary to lock up the circuit locally while the call indicator impulses are being received and absorbed. This is accomplished through the operation of relay 208 as previously described. In order that the trunk may be released if the call should not progress in a normal manner, with relay 208 operated a circuit is established upon the operation of relay 20| and prior to the operation of relay 2| 4 as soon as the interrupter 2 I6 makes its right contact, which may be traced from ground at the left contacts of relay 2| 4, outer left contacts of relay 20|, right contact of interrupter 2I6, upper contacts of relay 208 to battery through the winding of relay 2 I1. Relay 2I1 thereupon operates, locks over its lower contacts to ground at the middle upper contacts of relay 208, and prepares at its upper contacts a short circuit for releasing relay 208. proximately ve seconds, during which interval all call indicator impulses should have been received and absorbed, if relay 20| has not released a circuit is established from ground at the left contacts of relay 2 I4, over the outer left contacts of relay 20 I, left contact of interrupter ZIE, upper front contacts of relay 2I1 to a point between resistance 209 and the winding of relay 208, whereby the winding of relay 208 is shunted and relay 208 releases to wipe out the call.

When the start relay 2I3 of the distributing circuit operates upon the seizure of the trunk of Fig. 2 as previously described or upon the seizure of other similar trunks it prepares a circuit extending from ground over its lower contacts, the lower normal contacts of key 2I2, conductor 220 to the outer right front contacts of relay 101 for a purpose to be later described and over its upper front contacts establishes a circuit extending from battery through the winding of relay 22|, upper contacts of relay 2I3, upper normal contacts of key 2I2, conductor 222, to ground at the right back contacts of alarm relay II00, if there is anvannouncing machine in service at the central bureau ready to transmit announcements. Relay 227|, upon operating, establishes over its upper front contacts and the lower back contacts of relay 223 circuits in parallel through a plurality of relays, such as 224, which in turn cause the operation of a plurality of relays such as 225, each serving ten trunks. As many relays, such as 225, are provided as are necessary to serve all of the announcement trunks. At its middle front contacts relay 22| also establishes a circuit extending over the upper back contacts of relay After ap- 

